Shaft seal



July 25,1944. I R. c. -RE INHA'RDT ETAL SHK'FT SEAL Filed May 21, 1941INVENTORS E161. Z kobe r/ C. Rzl'n/mr'07 Raynor- L. J nas BY Lowrance1V. Black/vars? W 42 W A TTORNEVS Jl lgzisaviewpa lyin Patented July 25,1944 UNITED STATES PATENT ormcs Robert c. Jones, in...

rence N. Blackhurst, llidlan Dow Chemical Company. Midland.

to The d, Mich, anignors Mich.,a corporation of Michigan -Applicationllayzi, 1941. Serial No. 394,398

3 Claims. (Cl. 286-11) This invention relates to a shaft seal, and moreA particularly concerns an improved bellows-type seal for preventingleakage along a rotatable shaft extending into a pressure vessel.

It is a problem to seal the opening in the wall of a vessel throughwhich a rotatable shaft protrudes in such a manner as to prevent leakageor loss of pressure and at the same time to avoid undue shaft frictionwhich generates heat, causes loss of power, and may even lead to injuryof the shaft or the sealingdevice, or b9th. One construction commonlyused as a seal for this purpose is of the so-called bellows-type inwhich the seal is made by 'twoopposed annular bearing surfaces one ofwhich is mounted on a shoulder formed on the shaft, and the other ofwhich is held pressed againstthe surface by means of a flexiblegas-tight metal bellows which surrounds the shaft and is fastened to thewall of the vessel; in most instances a lubricant is maintained withinthe 'bellows. While the known seals of this type are useful for avariety of purposes, they rarely can be applied satisfactorily topressure vessels employed in chemical reactions since contamination ofthe vessel contents by ,the seal lubricant is a frequent occurrence. Inaddition, in the case of vessels designed to contain corrosive orcondensible vapors, seals of this character are virtually useless, sincethese vapors invariably-tend to attack the carefully machined sealingsurfaces and render them no longer fluid tight. v a

In view of this difficulty, it is an object of the invention to providea shaft seal which retains the advantages of the bellows-type.construction, but which also is not subject to the disadvantagesthereof, and may satisfactorily be applied to shafts protruding frompressure vessels adapted to contain corrosive fluids without danger ofleakage or of contamination of the vessel con.- tents ment. The basicelement for one sub-assembly is the wall of the pressure vessel or anextension thereof. and the basic element for the other subassembly isthe vshaft itself. The shaft seal is formedby placing a portion of onesub-assembly The invention may bestbe explained .with ref-.

within the other, whereby a sealing ring of one assembly seats upon abearing surface borne by the other, these two opposed surfacesconstituting the seal proper.

In Fig. 1, "the seal according to the invention is employed to preventleakage between the upper wall ll of a pressure vessel and a verticalrotatable "shaft ll extending through an opening in the wall II, andconsists essentially of a lower stationary sub-assembly indicatedgenerally as A and an upper sub-assembly B, the latter being v ii ofrectangular cross-section, which serves as a bolt-circle for thecapscrews l6 holding the entire sub-assembly'A to the vessel wall it;the

. inner vertical surface of this shoulder i5 is highly finished toprovide agrbearing surface, as herein.- after further explained. Seatedin a circular groove in the upper face of the flange plate I! andencircling the shaft li-concentric therewith at a position outside thesleeve I4 is an annular member ll of wear-resisting material, the upperface 2i of which is finished as a bearing surface. A fluidinlet line itis formed in the flange plate leading from the outside to a pointbetween the bearing member I1 and the sleeve II, the inlet providedonits lower face with a highly flnbeing normally closed with ascrew-plug it.

The upper rotatable sub-assembly B essentially comprises a sealing ring28 which encircles the shaft Ii outside the stationary sleeve l4, and isished annular bearing surface 22 adapted to oppwe and-press"against thecorresponding stationary bearing surface 2i already mentioned,

these two surfaces together forming a running seal. The sealing ring}.is caused to rotate with .the shaft II by means of driving pins 2! whichextend into holes 24 drilled'in thering 20 in such manner as to receivethe pins in an easily slideable'flt, and is steadied in its rotation bya bearing surface 28 on its puter periphery which rides on thestationary flange shoulder '15. The pins 23 are threaded at their upperend into a collar The periphery of the flange vplate is formed with araised annular shoulder a bell 21 which is secured at its top to theshaft II by a fluid-tight joint in such position as to enclose the upperend of the sleeve I4. The sealing ring 20 is prevented from unseating bythrust springs 28 which flt around the pins 23 and may be adjusted bymeans of lock nuts 29. Extending between the bearing ring 20 and thebell 21 and encircling the sleeve I4 is a hollow cylindrical metalbellows 30 sealed to both the ring and the bell. The bellows III servesto maintain the ring 20 in fluid-tight connection with the shaft II, andyet at the same time is sumciently flexible so that wobbling and othereccentricities in the rotation of the shaft are not transmitted to thering 20 and hence do not tend to affect the tightness of the seal formedbetween the ring 20 and the annular bearing II.

The bellows 30 and the bell 21 to which it is attached constitute one oftwo liquid-retaining members, the other of which is the stationarysleeve I4 which extends within the bellows 30 out of contact therewith,these two members together forming a liquid reservoir 3| which is incommunication with the interior of the vessel through the shaft opening.This reservoir 3| is normally filled to a level above the bellows by alubricant sealing fluid, such as oil, introduced by way -0f the fluidinlet line ll in the stationary flange- In operation of the seal shownin Fig. 1, when the shaft II is rotating, the bell 21, the bellows 30,the sealing ring 20, and attached parts, are also in rotation, while theflange I2, annular bearing surface 2|, and sleeve I4 remain stationary.The seal proper is formed solely by the two opposed relativelyrrotatable highly finished bearing surfaces 2| and 22, one of which is influid tight connection with the shaft II and the other with the sleeveI4. These sealing surfaces 2| and" 22 and the bellows 30 are protectedfrom direct contact with any corrosive vapors within the vessel III bythe sealing liquid, which also acts as a lubricant for the movingsurfaces 2| and 22.

The seal illustrated in Fig. 2 is likewise designed to prevent leakagebetween a vessel IIII and a shaft extending through an opening therein,but differs from the construction of Fig. 1 in that the upper sealingring and attached bellows are stationary, whilev the lower sealingsurface is rotatable with the shaft m.

As shown, the rotatable portion ofthe seal comprises a lower annularbearing surface |2| encircling the shaft III and embedded in a collarII2 mounted thereon, and an elongated hollow cylindrical liquidretaining sleeve Ill welded to the collar 2 at its periphery andextending upwardly therefrom.

face I22 adapted tooppose and press against the rotatable lower bearingsurface |2|, these two surfaces tbgether forming a running seal. Thesealing ring I2! is steadied by an inner shoulder I25 which is adaptedto fit closely around the shaft, and is held stationary by a hollowcylindrical mounting I21 encircling the shaft III, being carbon orgraphite composition.

I 2,354,478 26 formed integrally with the lower portion of sealed to themounting by a flexible metal bellows I30. A helical thrustspring In isseated on the bottom of the mounting I21 and extends downwardly outsidethe bellows I to hold the sealing ring I20 against the rotatable bearingsurface |2|. The mounting I2! is formed with an upper flange which restson the housing I, being sealed thereto by a gasket I" and held inposition by a ring I21. which may be tightened by bolts I38. The upperflange is formed with a fluid inlet IIB leading from the outside to apoint adjacent the outside of the bellows, this inlet being normallyclosed by a plug III. In this seal, the space IlI between theliquidretaining sleeve Ill and the bellows I" and its mounting I2'Iconstitutes a liquid reservoir in communication with the interior of thevessel through the shaft opening. Lubricant sealing liquid is maintainedin this reservoir at a level above the top of the bellows |2|, beinginjected through the fluid inlet III and serving in 1mm cate the sealingsurfaces |2| and I22 as' well as to protect them from contact with anyvapors which ma be generated in the vessel,

. In either embodiment of the invention illustrated, the opposedrelatively rotatable annular bearing surfaces must be finished withconsiderable care, since the effectiveness of the seal depends upon anaccurate flt ofthese surfaces one on the other. Ordinarily they are madefrom an anti-friction bearing material such as leaded bronze, porousbronze impregnated with oil, or a The materials utilized must havesufficient mass to resist warping tendencies incidental to the assemblyof the' seal and the high temperatures encountered in service. Thebearings should be designed with particular care so that adequatelubrication of the entire sealing surface is obtained while at the sametime the surface area should be suiilciently great to avoid excessivebearing loads. In flnishing the opposed surfaces, 1. e., that of thesealing ring and the annular bearing, some special process such aslapping is usually found to be desirable.

The invention provides an improved seal for pressure vessels whichretains all the advantages of the bellows- 1am seal but which also isfully protected against attack by corrosive vapors within the vessel,and does not tend to contaminate the contents thereof. The seal is alsoread ily adaptable to use on evacuated vessels.

Other means of applying the principle of the invention may be employedinstead of those ex- 'plained, change being made as regards the details,provided the elements recited in any of the following claims, or thesubstantial equivalent thereof, be employed.

We claim:

1. In combination with a closed vessel having a shaft opening in the topwall thereof and a vertical rotatable shaft extend-ins through theopening, a shaft seal comprising: two opposed relatively rotatableannular bearing members encircling the shaft, one above the other. thelower member being mounted on the shaft and in fluid-tight relation withit; a'hollow liquid retaining member encircling the shaft above thebearing members, said member beinl QNed at its lower end to the upperbearing member and at its upper end being flrmly mounted in fluidtightrelation with the vessel wall; and a second hollow liquid-retainingmember-mounted on the shaft co-axial therewith and surrounding the flrstliquid-retaining member, the lower end of said retaining member being influid-tight relation with the aforesaid lower bearing member,

the space between the retaining members constituting a liquid reservoirin open communication with the'interior of the vessel through the shaftopening in the vessel wall.

2. In combination with a closed vessel having a shaft opening in the topwall thereof and a vertical rotatable shaft extending through theopening, a shaft seal comprising: two opposed relatively rotatableannular bearing members encircling the shaft, one above the other, thelower member being'mounted on the shaft and in fluid-tight relation withit; 'a substantially cylindrical metal bellows encircling the shaftabove thebearing members, said bellows being sealed at its lower end tothe upper bearing 3. In combination with a closed vessel having -a shaftopening inthe top wall thereof and a vertical rotatable shaft extendingthrough the opening, a shaft seal comprising: two opposed relativelyrotatable annular bearing members en'- circling the shaft, one above theother, the lower member being mounted on the shaft and in fluidtightrelation with it; a substantially cylindrical metal bellows encirclingthe shaft above the bearing members, said bellows being sealed at itslower end to the upper bearing member and,

at its upper end being firmly mounted in fluidtight relation with thevessel wall; a hollow, cylindrical, liquid-retaining membermounted onthe shaft eo-axial therewith and surrounding the bellows, the lower endof said retaining member being in fluid-tight relation with theaforesaid member and at its upper end being flrmly mountcation with theinterior of the vessel through the shaft open'ingin the vessel wall.

lower bearing member, the space between the bellows and retaining memberconstituting a liq-- uid reservoir in open communication with theinterior of the vessel through the shaft opening in the vessel wall; andmeans for introducing lubricant sealing liquid into the said reservoir.

ROBERT C. REINHARDT. RAYNOR L. JONES. LAWRENCE N. BLACKHURST.

